Revert "ANDROID: sched: Keep sched_class::set_cpus_allowed stable"

This reverts commit c61797f241.

This series is responsible for a functional regression with task
affinity failing to take into account offline CPUs. Although this has
been reported upstream, work to fix the problem is ongoing and we're
better off reverting these changes from android13-5.15.

Link: https://lore.kernel.org/lkml/20230131221719.3176-1-will@kernel.org/
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 263926519
Bug: 264940090
Change-Id: I0a4074f52208da12efea22c8ffcd32ac76c458ad

kernel/sched/core.c

@@ -2568,18 +2568,7 @@ __do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
 	if (running)
 		put_prev_task(rq, p);
 
-	/*
-	 * XXX: ANDROID: we can't use sched_class::set_cpus_allowed() here
-	 * because it doesn't take a struct affinity_context as parameter for
-	 * GKI KMI stability reason -- see b/254812379. To avoid the problem,
-	 * let's hardcode the indirection here and hope for the best. The only
-	 * other potential users of p->set_cpus_allowed() will be in vendor
-	 * modules.
-	 */
-	if (likely(p->sched_class != &dl_sched_class))
-		set_cpus_allowed_common(p, ctx);
-	else
-		set_cpus_allowed_dl(p, ctx);
+	p->sched_class->set_cpus_allowed(p, ctx);
 
 	if (queued)
 		enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);

kernel/sched/deadline.c

@@ -2341,7 +2341,8 @@ static void task_woken_dl(struct rq *rq, struct task_struct *p)
 	}
 }
 
-void set_cpus_allowed_dl(struct task_struct *p, struct affinity_context *ctx)
+static void set_cpus_allowed_dl(struct task_struct *p,
+				struct affinity_context *ctx)
 {
 	struct root_domain *src_rd;
 	struct rq *rq;
@@ -2373,18 +2374,6 @@ void set_cpus_allowed_dl(struct task_struct *p, struct affinity_context *ctx)
 	set_cpus_allowed_common(p, ctx);
 }
 
-static void set_cpus_allowed_dl_cb(struct task_struct *p,
-				   const struct cpumask *new_mask,
-				   u32 flags)
-{
-	struct affinity_context ac = {
-		.new_mask  = new_mask,
-		.flags     = flags,
-	};
-	WARN_ONCE(1, "Unexpected use of dl_sched_class::set_cpus_allowed()");
-	set_cpus_allowed_dl(p, &ac);
-}
-
 /* Assumes rq->lock is held */
 static void rq_online_dl(struct rq *rq)
 {
@@ -2577,7 +2566,7 @@ DEFINE_SCHED_CLASS(dl) = {
 	.pick_task		= pick_task_dl,
 	.select_task_rq		= select_task_rq_dl,
 	.migrate_task_rq	= migrate_task_rq_dl,
-	.set_cpus_allowed       = set_cpus_allowed_dl_cb,
+	.set_cpus_allowed       = set_cpus_allowed_dl,
 	.rq_online              = rq_online_dl,
 	.rq_offline             = rq_offline_dl,
 	.task_woken		= task_woken_dl,

kernel/sched/fair.c

@@ -11842,7 +11842,7 @@ DEFINE_SCHED_CLASS(fair) = {
 	.rq_offline		= rq_offline_fair,
 
 	.task_dead		= task_dead_fair,
-	.set_cpus_allowed	= set_cpus_allowed_common_cb,
+	.set_cpus_allowed	= set_cpus_allowed_common,
 #endif
 
 	.task_tick		= task_tick_fair,

kernel/sched/idle.c

@@ -516,7 +516,7 @@ DEFINE_SCHED_CLASS(idle) = {
 	.balance		= balance_idle,
 	.pick_task		= pick_task_idle,
 	.select_task_rq		= select_task_rq_idle,
-	.set_cpus_allowed	= set_cpus_allowed_common_cb,
+	.set_cpus_allowed	= set_cpus_allowed_common,
 #endif
 
 	.task_tick		= task_tick_idle,

kernel/sched/rt.c

@@ -2635,7 +2635,7 @@ DEFINE_SCHED_CLASS(rt) = {
 	.balance		= balance_rt,
 	.pick_task		= pick_task_rt,
 	.select_task_rq		= select_task_rq_rt,
-	.set_cpus_allowed       = set_cpus_allowed_common_cb,
+	.set_cpus_allowed       = set_cpus_allowed_common,
 	.rq_online              = rq_online_rt,
 	.rq_offline             = rq_offline_rt,
 	.task_woken		= task_woken_rt,

kernel/sched/sched.h

@@ -2205,9 +2205,7 @@ struct sched_class {
 
 	void (*task_woken)(struct rq *this_rq, struct task_struct *task);
 
-	void (*set_cpus_allowed)(struct task_struct *p,
-				 const struct cpumask *newmask,
-				 u32 flags);
+	void (*set_cpus_allowed)(struct task_struct *p, struct affinity_context *ctx);
 
 	void (*rq_online)(struct rq *rq);
 	void (*rq_offline)(struct rq *rq);
@@ -2320,20 +2318,8 @@ extern void update_group_capacity(struct sched_domain *sd, int cpu);
 
 extern void trigger_load_balance(struct rq *rq);
 
-extern void set_cpus_allowed_dl(struct task_struct *p, struct affinity_context *ctx);
 extern void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx);
 
-static inline void set_cpus_allowed_common_cb(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
-{
-	struct affinity_context ac = {
-		.new_mask  = new_mask,
-		.flags     = flags,
-	};
-
-	WARN_ONCE(1, "Unexpected use of sched_class::set_cpus_allowed()");
-	set_cpus_allowed_common(p, &ac);
-}
-
 static inline struct task_struct *get_push_task(struct rq *rq)
 {
 	struct task_struct *p = rq->curr;

kernel/sched/stop_task.c

@@ -134,7 +134,7 @@ DEFINE_SCHED_CLASS(stop) = {
 	.balance		= balance_stop,
 	.pick_task		= pick_task_stop,
 	.select_task_rq		= select_task_rq_stop,
-	.set_cpus_allowed	= set_cpus_allowed_common_cb,
+	.set_cpus_allowed	= set_cpus_allowed_common,
 #endif
 
 	.task_tick		= task_tick_stop,